The instant invention relates to a device for detection of breakage of textile fiber slivers before delivery to a draw frame. The device must detect the sliver breakage in presented fiber slivers near or within a feeding device for textile fiber slivers, i.e. before entry into the draw frame.
The fiber slivers are taken from cans and are conveyed via a feeding device to the roller pair on the intake table of the drafting rollers. The feeding device is located in a section before the intake table of drafting rollers. On both sides or on only one side of the feeding device, cans with the fiber sliver to be processed are placed. The fiber sliver of each can is pulled straight up from the can and is deflected by the feeding device by an angle of approximately 90.degree. in the direction of the draw frame. The fiber slivers of all cans are conveyed parallel to each other by the feeding device, with the fiber slivers being conveyed at a higher level than the drafting rollers. The fiber slivers leave the feeding device by being conveyed to the draw frame away from the feeding device at a downward slope. During the transportation of the fiber slivers being presented to the draw frame, individual fiber slivers may break. The cause is usually a defect of the sliver stemming from the way it was deposited. For this reason a monitoring device is installed in the conveying path of the fiber sliver to detect and signal any sliver breakage. The signal for a sliver breakage causes the draw frame to stop so that the operating personnel can piece the band ends before they enter the draw frame. The monitoring device may be installed inside the feeding device or between the feeding device and the draw frame.
A sliver breakage of the running sliver is detected by letting the sliver end drop down from its conveying path after leaving the feeding device to be detected by the monitoring section of the monitoring device. The monitoring device operates in a known manner according to the optical light barrier principle. Such a known monitoring device between draw frame and feeding device is shown in the prospectus "Strecken", September 1991, page 11, of Rieter Spinning Systems.
With the high prevailing intake speeds of the fiber sliver the problem arises that not every sliver breakage is certain to be detected by the monitoring device. At high fiber sliver intake speeds, it occurs that the sliver end reaches a drop level at the level of the monitoring sections only after the monitoring device, so that the dropping sliver end was not able to trigger a signal. In such a case, the sliver end runs through the charging or contact rollers in the intake of the draw frame and is only there detected as a sliver breakage. This has the disadvantage that the sliver ends can no longer be pieced together, but a new sliver start must be threaded. This is much more time consuming than the piecing of sliver ends before entry into the draw frame.